1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device in which a pair of substrates are opposed to each other with a predetermined gap interposed therebetween by spacer materials and a liquid crystal compound is retained in the gap.
2. Description of the Related Art
In recent years, liquid crystal display devices are widely used as small-sized display devices and display terminals for so-called OA equipment. These kinds of liquid crystal display devices basically include a so-called liquid crystal panel (also called a liquid crystal cell) in which a layer of a liquid crystal compound (or a liquid crystal layer) is interposed between a pair of substrates at least one of which is made of a transparent glass plate, a plastic substrate or the like. Such a liquid crystal panel is generally classified into a type (simple matrix) which selectively applies voltages to various kinds of pixel-forming electrodes formed on the substrates of the liquid crystal panel to change the alignment direction of liquid crystal molecules which constitute a liquid crystal compound of a predetermined pixel portion, thereby forming pixels, and a type (active matrix) in which various kinds of electrodes and pixel-selecting active elements are formed on the substrates of the liquid crystal panel so that selection is made from these active elements to change the alignment direction of the liquid crystal molecules of pixels lying between pixel electrodes and reference electrodes connected to the active elements, thereby forming the pixels.
In general, the active matrix type liquid crystal display device adopts a so-called vertical electric field mode in which an electric field for changing the alignment direction of its liquid crystal layer is applied across an electrode formed on one of its substrates and an electrode formed on the other.
On the other hand, a liquid crystal display device of so-called in-plane-switching mode (abbreviated to IPS mode) in which the direction of an electric field applied to its liquid crystal layer is made parallel to its surface surfaces has been put to practical use. As a disclosed example of this in-plane-switching mode of liquid crystal display device, a liquid crystal display device constructed to obtain a very wide viewing angle by using comb-teeth electrodes on one of two substrates has been known (Japanese Patent Publication No. 21907/1988 and U.S. Pat. No. 4,345,249).
A liquid crystal panel for use in this kind of liquid crystal display device is constructed so that spacers are interposed in the gap between a pair of insulating substrates in which a liquid crystal compound is sealed, in order to hold the gap at a predetermined value.
In general, related-art spacers employ spherical spacers made of a material which contains resin or glass, or spherical spacers made of a similar material and subjected to surface treatment with a coloring agent, an adhesive or an alignment treatment agent, and such spacers are scattered between the electrode-side inner surfaces of the insulating substrates by a static electricity dispersion method, a semi-dry spray method or the like.
In addition, it has also been proposed that instead of such spherical spacers, a predetermined pattern of column-shaped spacers (projections) is formed by a photolithographic technique, a printing technique or the like on at least a part of an area (non-pixel part) shielded from light by a light shield part (a light shield film or a black mask) (Japanese Patent Laid-Open Nos. 325298/1995 and 286194/1996).